Electric Power Assisted Steering (EPAS or EPS) systems employ an electric motor to assist the driver in providing the amount of torque required to control the direction of the steered wheels of a vehicle for controlling the direction of the vehicle. Sensors disposed within the vehicle are used to detect the motion and torque of the steering wheel. A computer module calculates an amount of assistive torque to apply and instructs an electric motor, optionally, disposed on a rack between the steered wheels of the vehicle, (i.e. the wheels that are being moved) to apply that assistive torque. The steering system allows varying amounts of assistance to be applied depending upon the driving conditions. For example, if the vehicle is travelling forwards (typically the steered wheels are leading); or if the vehicle is travelling in a reverse direction (typically the steered wheels are trailing); or if the vehicle is cornering, the amount of assistive torque applied might need to be different. Similarly, dependent upon the speed of travel, a different amount of assistive torque may be needed. Typically, greater assistance is needed at slower speeds, but at higher speeds a lower amount of assistive torque may be appropriate, otherwise the driver might find the vehicle difficult to handle. For a particular restricted set of pre-determined conditions the assistive torque to be applied is found in a look up table or is calculated.
It is desirable in certain applications to carefully control the driving experience and for the handling of the vehicle experienced by the driver to meet very high standards. In executive or luxury cars it is desirable to provide a smooth driving feel with a high sense of driver control. In vehicles of a more sporting nature, a different feel of vehicle handling may be desired. It may even be desirable to provide both characteristics within the same vehicle and allow the driver to select between driving modes. It is an object of the present invention to provide an improved EPAS system. The present invention seeks to improve upon the EPAS systems of the prior art by providing an EPAS system that may compensate for or otherwise mitigate some undesirable characteristics of known EPAS systems.